The present invention relates to musical instrument amplifier circuits and in particular to a modification for the pre-amp stage of a musical instrument amplifier which is incorporated by coupling the circuit to the socket of one of the amplifier tubes in place of the amplifier tube previously inserted in that socket.
Amplification of electronic signals generated by musical instruments at rock concerts and the like involve not merely amplification but also selected distortion of the signals to create various types of sound effects when the signal is applied to loud speakers. Because of the wide range of special effects and sound distortion characteristics which have been deemed desirable in rock concerts and the like, transistorized sound amplifiers are less desirable than tube type amplifiers because the desired distortion caused by tube amplification does not occur. Accordingly, the standard amplifiers used by instrumentalists such as rock artists in live performances is a tube amplifier such as a Marshals Master Volume Series Amplifier or other similar type of tube amplifier.
To illustrate, distortion can be caused by increasing the gain to drive the signal originating with the musical instrument to operate a greater percentage of the time in the fully saturated tube operating zone. This will result in clipping the signal which in turn causes significant distortion of the signal. Such distortion will cause the signal to exhibit considerably longer "sustain" characteristics than if the distortion was not present.
While conventional tube amplifiers are adequate to achieve many desired effects, musicians have exhibited considerable interest in sound effects which could be created by modifying the signal characteristics by modifying the electrical characteristics of the amplifier. Heretofore, such modifications have required dismantling of the amplifier and alteration of the amplifier's electrical circuitry at considerable expense. Even then, such changes are permanent requiring an artist to go to the expense and trouble of having different amplifiers for the different effects which might be desired in a musical concert.
The present invention solves this problem by providing a separate modification unit which may be coupled to the conventional tube amplifier by simply unplugging one of the tubes in the pre-amplifier stage and plugging a separate modification unit into that socket via a suitable cable to receive dc and ac power from the amplifier and provide a modified electronic signal back to the amplifier where it is amplified in the power amplifier stage and supplied to suitable speakers.
The modification unit could be of any type and could be designed in any desired way to modify the signal from the electrical instrument. In an illustrative embodiment, a modification unit is interconnected to replace the gain amplifier of the pre-amp stage of a Marshals Master Volume Series amplifier. The particular modification provides for a significant increase in gain in the signal which results in distortion of the signal by operating the circuit substantially in saturation thereby causing signal clipping and hence distortion. The result is the ability to greatly increase the sustain characteristics of the signal.
The present invention also enable easy incorporation of conventional effects circuits such as the Rocktron Hush Unit circuit to provide noise reduction. Such circuits may be easily plugged into the an effects plug in the modification unit to provide the desired effect.